The present invention relates to an electrolyte composition excellent in durability and a charge-transporting capability, a photoelectric conversion device comprising the electrolyte composition, and a photo-electrochemical cell composed thereof. The present invention also relates to a novel imidazolium compound and a novel pyridinium compound, which can be used for the electrolyte composition.
Conventionally, an electrolysis solution prepared by dissolving an electrolyte salt in a solvent has been used as an electrolyte for electrochemical devices such as a cell, a capacitor, a sensor, a display device, a recording device, etc. However, the electrochemical device comprising the prior art electrolysis solution often causes leakage of the solution during long-term operation or storage to be unreliable.
Nature, vol. 353, pp. 737-740 (1991), U.S. Pat. No. 4,927,721, etc. disclosed a photoelectric conversion device comprising dye-sensitized semiconductor particles, and a photo-electrochemical cell composed thereof. However, since the device also comprises the electrolysis solution in a charge-transporting layer, there is still a fear that its photoelectric conversion efficiency is extremely lowered, or its function is lost by leakage or depletion of the electrolysis solution during the long-term operation or storage.
Under these circumstances, International Patent No. 93/20565 disclosed a photoelectric conversion device comprising a solid electrolyte. Further, Nippon Kagaku Kaishi, 7, 484 (1997), Japanese Patent Laid-Open No. 7-2881142, Solid State Ionics, 89, 263 (1986) and Japanese Patent Laid-Open No. 9-27352 proposed a photoelectric conversion device using a solid electrolyte comprising a poly(ethylene oxide)-based, cross-linked polymer. However, the devices using the solid electrolyte are insufficient in photoelectric conversion characteristics, especially short-circuit current density. Additionally, durability of the devices is also insufficient.
Further, disclosed in WO 95/18456, Japanese Patent Laid-Open No. 8-259543, Denki Kagaku, 65, 11, 923 (1997), etc. is a method where a pyridinium salt, an imidazolium salt, a triazolium salt, etc. is used as the electrolyte for the photoelectric conversion device to prevent the leakage and depletion of the electrolytic solution. The salts are molten salts which are liquid at room temperature. The durability of the device is improved because solvents for dissolving the electrolyte such as water and organic solvents are not necessary or needed in only a little amount. However, the device using the molten salt generally has such a defect as a low photoelectric conversion efficiency.
An first object of the present invention is to provide an electrolyte composition excellent in durability and a charge-transporting capability, a photoelectric conversion device comprising the electrolyte composition that exhibits high durability and excellent photoelectric conversion properties, and a photo-electrochemical cell composed thereof.
Another object of the present invention is to provide a novel imidazolium compound and a novel pyridinium compound, which can be used for the electrolyte composition.
As a result of intense research in view of the above objects, the inventors have found that an electrolyte composition comprising a compound having a substituent containing repetition of a substituted or unsubstituted ethyleneoxy group at a particular position is excellent in the durability and the charge-transporting capability. The present invention has been accomplished by the finding.
Thus, an electrolyte composition of the present invention comprises a compound represented by the following general formula (1): 
wherein R represents a substituent containing a xe2x80x94(CR1R2xe2x80x94CR3R4xe2x80x94O)nxe2x80x94 bond (in which R1 to R4 are independently a hydrogen atom or an alkyl group, n being an integer of 2 to 20); Q represents an atomic group forming an aromatic cation having a 5- or 6-membered ring structure with a nitrogen atom, and may have a substituent; and Xxe2x88x92 represents an anion. The electrolyte composition can be preferably used for a photo-electrochemical cell.
A photoelectric conversion device of the present invention has an electrically conductive layer, a photosensitive layer, a charge-transporting layer and a counter electrode, and the charge-transporting layer comprises the electrolyte composition of the present invention. The photoelectric conversion device exhibits the high durability and the excellent photoelectric conversion properties.
Further, a photo-electrochemical cell of the present invention comprises the photoelectric conversion device.
With respect to the electrolyte composition, the photoelectric conversion device and the photo-electrochemical cell of the present invention, the durability, the charge-transporting capability and the photoelectric conversion properties are further improved by satisfying any of the following conditions.
(1) Q preferably has a substituent containing a xe2x80x94(CR1R2xe2x80x94CR3R4xe2x80x94O)nxe2x80x94 bond (in which R1 to R4 are independently a hydrogen atom or an alkyl group, n being an integer of 2 to 20).
(2) Q is preferably composed of atoms selected from the group consisting of carbon, hydrogen, nitrogen, oxygen and sulfur atoms.
(3) The 5- or 6-membered ring formed by Q is particularly preferably an imidazole ring or a pyridine ring.
(4) It is preferable that the compound represented by the general formula (1) is further represented by the following general formula (2) or (3): 
wherein R5 represents a substituent containing a xe2x80x94(CR1R2xe2x80x94CR3R4xe2x80x94O)nxe2x80x94 bond (in which R1 to R4 are independently a hydrogen atom or an alkyl group, n being an integer of 2 to 20); R6 to R10 independently represent a hydrogen atom or a substituent; Xxe2x88x92 represents an anion; and two or more of said R5 to R10 may be bonded together to form a ring.
(5) n in the general formula (1), (2) or (3) is preferably an integer of 2 to 6.
(6) The total number of xe2x80x94CR1R2xe2x80x94CR3R4xe2x80x94Oxe2x80x94 bonds (in which R1 to R4 are independently a hydrogen atom or an alkyl group) in the compound represented by the general formula (1) is preferably 4 to 6.
(7) Xxe2x88x92 is preferably Ixe2x88x92, Nxe2x88x92(CF3SO2)2, BF4xe2x88x92, Raxe2x80x94COOxe2x88x92 (in which Ra is a hydrogen atom, an alkyl group, a perfluoroalkyl group or an aryl group), Rbxe2x80x94SO3xe2x88x92 (in which Rb is an alkyl group, a perfluoroalkyl group or an aryl group) or SCNxe2x88x92, more preferably Ixe2x88x92.
(8) It is preferable that the electrolyte composition further comprises an iodine salt in addition to the compound represented by the general formula (1). A cation of the iodine salt is preferably a nitrogen-containing aromatic cation having a 5- or 6-membered ring structure.
(9) In the case where Xxe2x88x92 is Ixe2x88x92, it is preferable that the electrolyte composition comprises a salt containing an anion selected from the group consisting of Nxe2x88x92(CF3SO2)2, BF4xe2x88x92, Raxe2x80x94COOxe2x88x92 (in which Ra is a hydrogen atom, an alkyl group, a perfluoroalkyl group or an aryl group), Rbxe2x80x94SO3xe2x88x92 (in which Rb is an alkyl group, a perfluoroalkyl group or an aryl group) and SCNxe2x88x92. A cation of the salt is preferably a nitrogen-containing aromatic cation having a 5- or 6-membered ring structure.
(10) It is preferable that the electrolyte composition further comprises iodine.
(11) A solvent-content of the electrolyte composition is particularly preferably 10 weight % or less based on the total thereof.
(12) The photosensitive layer of the photoelectric conversion device preferably comprises semiconductor fine particles sensitized by a dye. The semiconductor fine particles are preferably composed of a metal chalcogenide, and the metal chalcogenide is preferably TiO2. The dye is preferably a metal complex dye and/or a methine dye.
A novel imidazolium compound represented by the following general formula (4): 
wherein R401 represents a substituent; R402 to R405 independently represent a hydrogen atom or a substituent; R401 and at least one of R402 to R405 independently contain a xe2x80x94(CR1R2xe2x80x94CR3R4xe2x80x94O)nxe2x80x94 bond (in which R1 to R4 are independently a hydrogen atom or an alkyl group, n being an integer of 2 to 20); X4xe2x88x92 represents Ixe2x88x92, Clxe2x88x92, Brxe2x88x92, Nxe2x88x92(CF3SO2)2, Nxe2x88x92(CF3CF2SO2)2, Cxe2x88x92(CF3SO2)3, BF4xe2x88x92, BPh4xe2x88x92, PF6xe2x88x92, ClO4xe2x88x92, Raxe2x80x94COOxe2x88x92 (in which Ra is a hydrogen atom, an alkyl group, a perfluoroalkyl group or an aryl group), Rbxe2x80x94SO3xe2x88x92 (in which Rb is an alkyl group, a perfluoroalkyl group or an aryl group) or SCNxe2x88x92; and two or more of R401 to R405 may be bonded together to form a ring,
and a novel pyridinium compound represented by the following general formula (5): 
wherein R501, represents a substituent; R502 to R506 independently represent a hydrogen atom or a substituent; R50, and at least one of R502 to R506 independently contain a xe2x80x94(CR1R2xe2x80x94CR3R4xe2x80x94O)nxe2x80x94 bond (in which R1 to R4 are independently a hydrogen atom or an alkyl group, n being an integer of 2 to 20); X5xe2x88x92 represents Ixe2x88x92, Clxe2x88x92, Brxe2x88x92, Nxe2x88x92(CF3SO2)2, Nxe2x88x92(CF3CF2SO2)2, Cxe2x88x92(CF3SO2)3, BF4xe2x88x92, BPh4xe2x88x92, PF6xe2x88x92, ClO4xe2x88x92, Raxe2x80x94COOxe2x88x92 (in which Ra is a hydrogen atom, an alkyl group, a perfluoroalkyl group or an aryl group), Rbxe2x80x94SO3xe2x88x92 (in which Rb is an alkyl group, a perfluoroalkyl group or an aryl group) or SCNxe2x88x92; and two or more of R501, to R506 may be bonded together to form a ring,
can be preferably used for the electrolyte composition.